Process of making insole sheets



Feb. 23, 1943.

H. G. LUMYBARD PROCESS OF MAKING INSOLE SHEETS Filed May 22. 1941 Patented Feb. 23, 1943 UNITED STATES PATENT OFFICE PROCESS or MAKING INSOLE smm'rs Henry G. Lumbard, Auburn, Maine Application May 22, 1941, Serial No. 394,611

4 Claims.

My invention relates to insoles for use in shoemaklng and consists in a process of making sheet material from which flexible insoles can be died out.

Composite sheets or strips of insole material as 'now commonly supplied to the trade include an intermediate section of relatively flexible material having skived edges cemented to bordering sections of relatively inflexible material, the edges of which are also skived to make spliced joints. Insoles may be laid out and cut or died from the composite sheet so that the toe and heel portions are formed in the stiff sections and the ball portion in the flexible center section of the sheet. One object of my invention is to eliminate the skived lap joint or splice formerly employed and provide therefor a smoother and stronger joint between the component sections of the insole.

An important advantage resulting from the use of my invention is the saving in material and labor which is obtained. Experiments have shown that the cost of making an insole sheet according to my invention is materially less than the conventional processes involving the use of skived splices.

Briefly speaking, the process of my invention comprises employing a bevel-edged cutting die to cut into the edges of the strip sections to be joined a series of mortises and tenons having enlarged thickened heads and tapering crosssections with marginal ribs formed in the material by the cutting blade, coating the edges with cement, inverting one piece with respect to the next and fitting the tenons of one strip section into the mortises of the other, and'then pressing the mortised joint to flatten the ribs and provide a smooth unbroken surface. A textile backing ,may be cemented across one surface of the joint to add additional strength to the joint and com- Fig. 4 is a view in cross-section of a joint after flattening pressure has been applied.

Some insole sheets provide a center section of flexible material bounded by stiffer edge sections, and others reverse the arrangement. Still others provide a stifi center section bounded by flexible strip sections which are in turn bounded by stiffer edge sections. From such composite sheets insoles can be cut out with zones of varying stiffness. The process of my invention is applicable to all kinds of insole sheets in which the edge portions of adjacent strip sections are joined.

Three sections make up the sheet shown in Fig. 2, two stiff sections l0 and I2, and an intermediate section l4. Preferably the intermediate section It is more flexible than either of the others. An insole l6 (shown in dotted lines) may be cut from the sheet so that it will have stifl heel and toe portions and a flexible ball I form a row of tenons 20 having downwardly tapering cross-sections and separated by mortises or recesses 22. The tenons 20 have enlarged heads and reduced neck portions so that the cut 'pieces when once joined cannot be separated by a horizontal pull but'require vertical separawhich makes a tapering cut displaces the mate-.

, rial, e. g., of the strips l0 and I2, and forms ribs or mounds l3 bounding the top of the cuts. No

. material is wasted, since each edge is suited for making a joint with another and interfltting edge of a difierent strip; thus the strips I0 and i2 may be cut from a'larger sheet, as suggested in Fig. 1. The cut edges are dipped or otherwise coated with a suitable cement 26, such as latex.

In making a sheet of insole material the intermediate strip [4 (or both the strips l0 and i2) is inverted so that the tenons thereof taper upwardly. Then the tenons 20 are fitted into the corresponding mortises 22. In practice there may, however, be initially some clearance between the assembled strips by reason of the tapered cross sections of the cut edges and the rounding of the edges where the die made its entry. The bevel-edged die or knife 18 is used primarily to provide clearance between the interlocked tenons suflicient to receive cement or adhesive. The flattening pressure subsequently applied to the joint forces the cement into the fibers of the material and makes a better bond. If the tapered tenons of one strip I4 were not inverted with respect to the tenons of the strips l and H, the tenons of the strips would not interflt by reason of the fact that the widest parts of the tenons of the strip ll, before inversion, are at the bottom whereas the widest portion of the recesses between the tenons of the strips l0 and l2 are at the top, and the sides of these recesses converge downwardly. Accordingly the narrowest portion of the tenons must be received in the narrowest portion of the recesses, which can be accomplished only by inverting one of the strips, with the result that the tenons of the inverted strip taper upwardly and the tenons of the uninverted strip, or strips, taper downwardly.

The joints when once formed are subjected to heavy pressure which flattens out the ribs formed by the die and forces the cement into the material to form a secure bond. The tenons are locked, by their shape, into the corresponding mortises and a firm, secure joint is thus effected. I have found that if a straight edged knife or die is used instead of a bevel-edged die, the most desirable results cannot be obtained because the fit is too close to accommodate the coating of cement.

The joint before the application of pressure is shown in Fig. 3, wherein the ribs or ridges I3 are clearly apparent, the rib on the strip l2 being on top of the joint, while the rib on the strip I4 is at the bottom thereof. Fig. 4 shows the appearance of the joint after pressure has been applied. Here the tapered edges have been straightened out, and the ribs have completely disappeared, the material thereof having been squeezed into the interstices of the joint. A thin backing sheet 30 may be cemented to the strip section ll to cover the area of both joints and to prevent vertical displacement of the mortises and tenons, although the inclusion of such a step is optional. The backing sheet 30 may be of paper, textile, or other thin flexible material.

jacent the cut edges where the bevel edge knife enters the material, coating the cut edge of each strip with cement, fitting the tenons of each strip into the recesses between the tenons of the other strip with the tenons of one strip tapering downwardly and the tenons of the other strip tapering upwardly, subjecting the strips to pressure to force the edges of the tenons together and to force the material of the ribs to flow into the adjacent interstices to leave a smooth outer surface at the joint, and then cementing on a backing of thin flexible material.

2. The process of making a composite sheet of sole material, which comprises cutting into an edge of separate dissimilar strips a series of alternating mortises and tenons having tapering heads and downwardly tapering cross-sections, raising ribs in the material adjacent the cut edges of the strips, cementing the edges of the mortises and tenons, inverting one of the strips so that its tenons taper upwardly, interfitting the mortises and tenons of the inverted strip and a strip having downwardly tapering tenons, flattening the joint thus formed by squeezing the material of the ribs into interstices of the joint, and securing a thin flexible piece of material to one surface of the joint.

3. The process of joining strips of insole material which comprises cutting into the edge of each strip a series of tenons having enlarged heads and tapering cross-sections, forming ribs in the material adjacent the cut edges of the strips, inverting one strip so that the taper of its tenons is complementary to the taper of the tenons on another strip, interfltting the tenons of the two strips, and applying flattening pressure to the joint thus formed to squeeze the material of the ribs into the interstices of the joint and provide Those skilled in the art will readily appreciate the applicability of the process of my invention to insole materials of various types.

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

1. The process of joining strips of insole material, which comprises employing a bevel edge knife to cut into the edge of each strip a series of identical tenons having reduced necks, the tenons being of downwardly tapering cross-section, forming marginal ribs in the material ada smooth surface.

4. The process of joining strips of insole sole material, which comprises cuttingin'to the edge of each strip a series of tenons having enlarged heads and downwardly tapering cross sections, forming ribs in the surface of the material adjacent the cut edges of the strips, applying cement to the edges of the strips, inverting one of the strips so that the tenons thereof taper upwardly, fitting the tenons of the inverted strip into the spaces between the downwardly tapering tenons of another strip and subsequently flattening the strips to force the material of the ribs into the joint to leave a smooth surface therefor.

- HENRY G. LUMBARD. 

